Transmission of pictures



Jan. 6, 1931. J, o, BENTLEY 1,788,227

TRANSMISSION OF PICTURES Filed Aug. 16, 1929 Inventor: V Jetson O Bentl'eg,

b5 WM His Attorney.

Patented Jan. 6, 1931 UNITED STATES PATENT OFFICE JETsoN o; BENTLEY, E BEACON, NEW YoRK, AssIGNoR o GENERAL ELECTRIC COM; PANY, A coRroRATIoN OF NEW YORK TRANsMissmN 0E PICTURES Application filedAugus't 16, 1929. Serial No. 386,270.

whereby a picture of good quality is promesh at the border and duced by means of a relatively limited range of modulation frequencies.

In the transmission of pictures it is customary to scan the picture along successive vertical lines, horizontal lines, or spirally shaped lines. These methods of scanning are satisfactory where the lines per inch can be made high enough to give fine details. It sometimes happens, however, that the apparatus must be operated within a limited rangeof frequencies. Under these conditions the picture is likely to be unsatisfactory for the reason that its details are too coarse. In accordance with my invention this difficulty is avoided by scannin the picture radially, so that the details 0 p the picture produced vary in fineness from the center to the perimeter. 1

If the number of lines per inch be considered as the mesh of the picture, a picture, produced in this waywould have a coarse a finer mesh at the center. The details will thus be exceptionally good near the center. Thus-assuming a circular picture which has a radius R and is scanned vertically with S lines per inch and a similar picture scanned radially, using the same total number of lines for the two pictures, it is found that the mesh of the radially scanned picture will be about thesame as that from the vertically scanned picture on the circumference of a circle whose radius is .637 R (R being the radius of the picture). To the eye it will appear that approximately of the picture is equal to or better in mesh than the vertically scanned picture. Actually 40.6% of the picture will be equal to or better in mesh than the verticallyscanned picture. There is thus produced a marked improvement in the central portion of the picture at a sacrifice of detail near the circumference. This lack of detail near the circumference appears as a loss of light intensity. This defect may be counteracted as hereinafter explained by increasing the ings 21 and width of the scanning beam as this beam approaches the edge of the picture.

My invention will be better understood from the following description when considered in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

The single figure of the drawing is a diagrammatic illustration of a picture transmitting apparatus wherein my invention has been embodied.

This apparatus includes a picture 10 upon which light is projected from a source 11 through a lens 12, a fixed gear 13, a rotatable disc 14, a slotted rotatable member 16 and a lens 17 The light reflected from the successive elemental areas of the picture or image is received by a plurality of light sensitive cells 18 through which it is converted into electrical impulses corresponding to the shade of these elemental areas. These impulses are utilized in a well known manner to control the output of the radio transmitter 19.

The member 16 is closed at one .end except fora slot 20, is in the form of a hollow cylinder, is mounted in bearings 21 and 22 and is arranged to be rotated by suitable means such as, a motor 23 to which it is geared through gears 24 and 25. At its closed end the member 16 is provided with a bearing 26 in which the shaft of the disc 14 is journaled. At the opposite end of this shaft a gear 27 is provided. Diametrically opposite the bearing 26 is provided a counterweight 28 for counter-balancing the weight of the bearing 26 and disc 14.

The operation of the apparatus will be readily understood without detailed explanation. As the member 16 rotates in the bear- 22 the shaft of the disc 14 is revolved and rotation of this disc isproduced due to the gear 27 which meshes with the stationary gear 13. The relation between the rotational speed of the'member 16 and the disc 14 is of course dependent on the gearing ratio. The member 16 rotates at a much slower speed than the disc 14 which is provided with a plurality of radial slots 29.

The light projected on the picture bearing/V,

screen 10 from the light source ll is dependent on the space relation between the slot 20 of the member 16 and the slots 29 of the disc 14. As each slot sweeps past the slot 20 a radial line is traced on the picture bearing member.

If the cylindrical member 16 is rotated at a speed of twenty-one revolutions per second and the ratio of gear 27 and gear 13 is 2 1, then the disc 14 will rotate at forty-two revolutions per second. Under these conditions the twelve slots in the disc 14 will sweep across the slot 20 twice for every revolution of the cylinder member 16. This will correspond to a twenty-four line picture and twenty-one pictures per second. As will be readily understood by those skilled in the art, any other desired combination of pictures per second and lines per picture may be readily secured.

It will be observed that the slot 20 in the cylindrical member 16 is comparatively narrow at its center and comparatively wide at its ends. By thus increasing the width of the slot from its center outwardly, the illumination near the edges of the picture is made substantially the same as at the center. The detail of the picture of course is not improved by making the illumination uniform throughout the picture, but the lack of detail near the edge of the picture is not likely to be objectionable where the picture is of good quality in its central area.

The embodiment of the invention illustrated and described herein has been selected for the purpose of clearly setting forth the principles involved. It will be apparent, however, that the invention is susceptible of being modified to meet the difierent conditions encountered in its use and I therefore aim to cover by the appended claims all modifications within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent .of the United States, is:

1. The method of picture transmission which comprises successively scanning a picture along radial lines, and increasing the sizeof the scanning beam near the ends of said lines. g

2. A picture transmitting a'pparatuscomprising a slotted member rotatable on an axis passing through the slot intermediate its ends, and a rotatable disc providedwith a plurality of radial slots arranged to be successively moved past the slot in said rota.-

table member.

3. A picture transmitting apparatus including a rotatable cylindrical member closed at one of its ends and provided with a. slot in said end, a bearing mounted on said rotatable member, a rotatable disc provided with a plurality of radial slots and with a shaft mounted in said bearing, and means for causing the slots in said disc to be successively gwept past the slot of said cylindrical mem- 4. A picture transmitting apparatus including a rotatable cylindrical member closed at one of its ends and provided with a slot in said end, a bearing mounted on said rotatable member, a rotatable disc provided with a plurality of radial slots and with a shaft mounted in said bearing, a stationary gear and a gear mounted on said shaft and arranged to cooperate with said stationary gear for causing the slots of said disc to be moved successively past the slots of said cylindrical member.

5. A picture transmitting apparatus including a rotatable cylindrical member closed at one of its ends andprovided with a slot in said end, a bearing mountedon said rotatable member, a rotatable disc provided with a plurality of radial slots and with a shaft mounted in said bearing, a; stationary gear and a gear mounted on said shaft and arranged to cooperate with said stationary gear for causing the slots of said disc to be moved successively past the slots of said cylindrical member, and driving means geared to said cylindrical member.

I 6. A picture transmitting apparatus comprising a rotatable member having a slot therein intersectin the axis of rotation, a rotatable disk having radial slots arran ed to be moved past the slot in the rotata le member, means for revolving the axis of rotation ofthe disk with said rotatable member and means for rotating said member and disk.

7. A picture transmitting apparatus com prising a rotatable member having a slot therein extending through and on opposite sides of the axis of rotation, the ends of the slot being wider than the intermediate portion, and a rotatable disk provided with a plurality of radial slots arranged to be successively moved past the slot in the rotatable member.

In witness whereof I have hereunto set my hand this 2d day of August, 1929.

JETSON O. BENTLEY. 

